Conventionally, a feedback feel from the steering wheel for conveying the steering state of the steering member is realized by a steering controller. That is, for example, a patent document, Japanese Patent Laid-Open No. 2014-213781 (Patent document 1) listed below discloses a change scheme that changes a rigidity component, a viscosity component, and an inertia component respectively used for torque generation according to a driver power rate, which is defined by a product of a steering torque and an angular speed of the steering shaft. More practically, for the mechanical impedance adjustment, an adjust torque is generated by changing those components according to the driver power rate.
Due to the lax response, i.e., a slow rise characteristics, of the driver power rate, which is caused by the mechanical backlash at a steer start time, e.g., loose connection and/or play between the components in the steering member slowly responding to the move of the steering mechanism on one end, the determination of switching between a steer-still state (i.e., staying at a steering wheel neutral/center position), a steer-away state (i.e., steering away from the neutral position) and a steer-back state (i.e., steering back to the neutral position) may be delayed from an actual switching of those states. Further, the driver power state tends to have a smaller value in the steer-back state than in the steer-away state. Therefore, when the driver power rate is used for the adjustment of the mechanical impedance factor, it may be difficult to adjust the mechanical impedance factor to an appropriate amount/quantity without delay from the change of state of the steering member.